Translation of abstract (English)

In the past, an ideal wavefield shape was assumed for performing size measurements by SMI microscopy. Disturbances of the wavefield, which modify the point spread function (PSF) of the SMI-microscope, were not considered. By using fluorescent objects with known dye distribution as reference objects an individual point spread function of the SMI microscope could be calculated for each size measurement. This measured point spread function was then used to calculate an individual R(S)-curve, which describes the dependence of the modulation contrast R from the object size S, for the size measurement. In this thesis, size measurements of microspheres with nominal diameters between 71 nm and 200 nm are shown. The results were compared with the results one would obtain without using reference objects. The usage of reference objects increased the accuracy of the size measurements significantly. In a second part of the thesis the shape dependence of the R(S)-curves is reduced by introduction of new size measures. These new size measures are not the total size anymore but a mean size of the dye distribution. For larger objects (d >= ca. 100 nm) the R(S)-curves stay shape dependent. By measuring the modulation contrasts R of those objects using two different excitation wavelengths it is possible to obtain a shape parameter. Knowing this parameter one can choose the correct R(S)-curve. Measurements on spheres with a nominal diameter of 190 nm are shown.